Polyolefin-based resins, typically polyethylene and polypropylene, have been widely used as general-purpose polymers because they are inexpensive, easy to process, strong, and light, while being produced at low cost. In particular, polypropylene, because of its excellent heat resistance and transparency, and favorable moldability, has been used for a wide range of applications in, for example, automotive parts, electrical and electronic components, industrial materials, furniture, stationery, miscellaneous daily goods, containers, packaging products, toys, leisure goods, and medical products.
The performance of polypropylene is closely associated with its crystalline form, crystallinity, crystalline morphology (size of spherulites), and the like. Thus, attempts have been made to control the molecular structure of polypropylene to thereby control the structures of the crystalline regions and the amorphous regions on the order of nanometers for the purpose of improving heat resistance, and mechanical properties, such as scratch-resistance and rubber elasticity.
Examples of known methods for improving mechanical properties, such as yield stress, necking stress, breaking stress, and breaking strain, without altering the molecular structure of a polymer include a method comprising modifying the processing technique, and a method comprising adding an elastomer, an inorganic filler, or the like to polypropylene to form a composite material. In particular, a high-performance approach using an additive can control a wide range of mechanical properties, and the approach is more economical than the technique for controlling the molecular structure of polypropylene.
Patent Document 1 discloses a composition consisting of polypropylene and a specific propylene-butene-ethylene copolymer, and the use of the composition for industrial shrink films and business-use wrap films.